1. Field of the Invention
The present invention relates to a radiographic image capturing system.
2. Description of the Related Art
Radiation detectors such as Flat Panel Detectors (FPDs), in which a radiation-sensitive layer is disposed on a Thin Film Transistor (TFT) active matrix substrate and that can convert radiation directly into digital data, have been put into practice in recent years. Accompanying this, the digitization of radiographic image capturing systems has advanced, and industries are transitioning from films and imaging plates to radiation detectors.
As compared with films and imaging plates, a radiation detector is expensive but results in high image quality, and further, has the advantage that images can be confirmed immediately. The popularization of radiation detectors is thereby advancing.
In radiographic image capturing, in addition to a method of capturing a region to be captured in a single image, there is also a method of capturing an elongated image by dividing the region to be captured (e.g., the entire body), that cannot fit into a single image, into plural images. In a radiographic image capturing system using a film or an imaging plate, a method is proposed of preparing plural cassettes that house films or imaging plates, and carrying out image capturing by partially overlapping the plural cassettes so as to make the surface area of image capturing larger (see, for example, Japanese Patent Applications Laid-Open (JP-A) Nos. 2002-85392 and 2005-257634). In a radiographic image capturing system using a radiation detector, not only is the radiation detector expensive, but also, the radiation detector is thick as compared with other systems. Therefore, there is proposed a method of carrying out exposure plural times while moving a single radiation detector and changing the range of image capturing so as to capture plural images, and thereafter, combining the plural images into a single image (see, for example, JP-A No. 2008-17965 and Japanese Patent Application National Publication No. 2006-500126).
However, the image capturing methods of JP-A No. 2008-17965 and Japanese Patent Application National Publication No. 2006-500126 require that exposure of X-rays be carried out plural times, and the image capturing time from the start of image capturing to the end thereof is long. Therefore, due to movement of the patient's body, combining of the images may fail, and patients with ailments must maintain the same body position over a long period of time. Therefore, a large burden is placed on the patient.
In recent years, there have been proposed thin cassettes (hereinafter also called “electronic cassettes”) that use a radiation detector. In the same way as with cassettes using films or imaging plates, an elongated image can be captured by connecting plural electronic cassettes, and the problem of the image capturing time becoming long can be overcome.
However, at a radiation detector, even in a state in which X-rays are not being irradiated, charges are generated due to dark current or the like, and the charges are accumulated in sensor portions that detect the X-rays. Therefore, during standby for imaging capturing, a radiation detector repeatedly and periodically carries out various image capturing preparation operations such as an eliminating operation that takes-out and eliminates the charges accumulated in the sensor portions.
It is not simple for plural radiographic image capturing devices, that repeatedly and periodically carry out such image capturing preparation operations, to simultaneously carry out capturing of radiographic images, which is different than in cases of using films or imaging plates.